senml_helpers.h

/*  _  __  ____    _   _ 
 * | |/ / |  _ \  | \ | |
 * | ' /  | |_) | |  \| |
 * | . \  |  __/  | |\  |
 * |_|\_\ |_|     |_| \_|
 * 
 * (c) 2018 KPN
 * License: MIT License.
 * Author: Jan Bogaerts
 * 
 * felper functions header
 */

#ifndef SENMLHELPERS
#define SENMLHELPERS

#ifdef __MBED__
    #include "mbed.h"
    #include "sstream"
#else
    #include <stream.h>
#endif
#include <senml_enums.h>
#include <math.h> 

#ifndef SENML_MAX_DOUBLE_PRECISION
#define SENML_MAX_DOUBLE_PRECISION 4
#endif // !SENML_MAX_DOUBLE_PRECISION

/** 
 * Internal helper struct that stores the base value to be used during rendering
 */
typedef union BaseData_t{
    uint64_t baseUint;
    int64_t baseInt;
    double baseDouble;
} BaseData;

/**
 * Internal helper struct that stores information needed during the rendering process
 */
typedef struct SenmlMemoryData_t{
    char* data;                             //pointer to the buffer that constitutes the input/output buffer
    int curPos;                             //current position in the buffer.
    int length;                             //length of the memory buffer.
} SenmlMemoryData;                          //a record used when the input for the parser or output for the renderer is a data blob stored in memory

/**
 *  Internal helper struct that stores information needed during the rendering process
 */
typedef union SenmlData_t{
    Stream* stream;
    SenmlMemoryData blob;
} SenmlData;                                //choose between input/outpu from a stream object (ex: direct input from uart) or from buffered data.

/**
 * Internal helper struct that stores information needed during the rendering process
 */
typedef struct StreamContext_t{
    bool dataAsBlob;                        //when true, data is from a memory blob, otherwise it comes from/goes to a stream object (ex: direct from/to uart)
    SenmlData data;                         //the data source to be parsed or destination to render to. can be from a stream or from data buffered in memory
    SenMLStreamMethod format;
    BaseData baseValue;                     //filled in when records need to adjust while rendering data.
    BaseData baseSum;
    SenMLDataType baseDataType;             //so we know which data type to use for baseValue and baseSum
} StreamContext;

/**
 * Internal data field used for the rendering process.
 */
extern StreamContext* _streamCtx;

/** 
 * Helper function for the generation process
 * write a double as string to the stream (_streamCtx).
 * @param f the value to print 
 * @param digits the nr of digits that should be printed after the comma.
 */
void printDouble(double f, unsigned int digits) ;

/**
 * Helper function for the generation process
 * convert the data array to base64 string and write to stream (_streamCtx)
 * @param data pointer to the binary data blob that needs to be rendered as base64 to the stream.
 * @param length the length of the data blob
 */
void printBinaryAsBase64(const unsigned char* data, unsigned int length);

/**
 * Helper function for the generation process
 * convert the unit to string and write to stream (_streamCtx).
 * @param unit the value to write as text to the stream.
 */
void printUnit(SenMLUnit unit);

/**
 * Helper function for the generation process
 * Writes the specified text to the stream (_streamCtx).
 * @param value the value to write
 * @param len the length of the value.
 */
void printText(const char*value, int len);



/**
 * Helper function for the parsing process
 * read a character from the current data stream (_streamCtx) 
 * takes into account that the stream might contain hex values
 */
int readChar();

/**
 * Helper function for the parsing process
 * peek a character from the current data stream.
 * takes into account that the stream might contain hex values.
 */
int peekChar();

/**
 * Helper function for the parsing process
 * flush and reset all input for the current data stream.
 */
void flush();

/**
 * Helper function for the parsing process
 * Reads the specified nr of characters from the stream (_streamCtx)
 * takes into account that the stream might contain hex values
 * @param buffer the buffer to store the values in.
 * @param len the nr of characters to read from the stream into the buffer. 
 *        If the input contains hex values, the actual nr of characters read from the
 *        stream is double this value.
 */
inline void readChars(unsigned char* buffer, int len)
{
    for(int i = 0; i < len; i++){
        buffer[i] = readChar();
    }
}

/**
 * Helper function for the parsing process
 * Checks if there is data available on the stream.
* Warning: THIS CAN BE PROBLEMATIC ON MBED SYSTEMS>
 */
inline bool charAvailable(){
    if(_streamCtx->dataAsBlob){
        return _streamCtx->data.blob.curPos < _streamCtx->data.blob.length;
    }
    else{
        #ifdef __MBED__
            return _streamCtx->data.stream->readable() != 0;      
        #else  
            return _streamCtx->data.stream->available() != 0; 
        #endif
    }
}

#endif // SENMLHELPERS